1. Field of the Invention
The present invention relates to an automatic two-stage switching valve in which a large flow rate and a small flow rate can be selectively obtained wherein a smooth transfer from the small flow rate to the large flow rate occurs.
2. Description of the Related Art
In general, in a known fluid system in which the flow rate is switched between a small flow rate (e.g., several cc/min.) and a large flow rate (several L/min.), a valve for the small flow rate and a valve for the large flow rate are provided in parallel, so that the valves are selectively opened. However, in the conventional fluid system, the two valves for the large flow rate and the small flow rate, parallel pipes thereof, and a three-way connector (T-connect or) are indispensable, and hence, the manufacturing cost and the number of the elements are increased, and the cost and space for the piping are also increased. Moreover, upon switching from the small flow rate to the large flow rate, it is necessary to provide a separate flow control valve in order to carry out a smooth change of the flow rate.